Cleft grafting is usually performed in the landscape or orchard on well established trees (up to full grown). Branches well up in the canopy of the tree are cut back with a saw at a point where they are one to several inches in diameter, for insertion of the scion(s). Often several branches on a single tree are cleft grafted as shown in the adjacent picture. Cleft grafts are often placed several to many feet above ground level.

Timing

: Cleft grafting is performed in the early spring just as the stock plant is beginning to become active (bud swelling, etc.). On the other hand, it is preferable to use scion wood that more or less fully dormant (phenologically several weeks "behind" the stock), which may be acomplished by collection scion wood earlier, during the winter, and storinging under refrigeration, in slightly moist cloth or other medium. This differential phenological activity between stock and scion allows vigorous callusing from the stock and later stages of graft union fomation at the point of stock/scion union, but the relative dormancy of the scion delays leafing out and hence minimizes scion water stress, which is critical before vascular continuity is established, i.e. before new xylem forms across the graft union to facilitate water transport from stock to sicon.

Applications

: When cleft grafting is performed several to many feet up from ground level, it is a topworking or highworking used for to change over (rework) an established fruit (scion) variety to a new (more desirable) variety, or to obtain multiple varieties on a single tree, or to insert a pollinizer branch for self incompatible trees like apple.

Reasons for Cleft Grafting

Clonal propagation

Difficult to clone by other methods

Economic advantage

Nurse grafting of slow to root species

Repair

Damaged or undesirble rootsystem

Overcome graft incompatibility

Girdled trunk

Topworking

X

Create unusual growth forms

Change scion variety

X

Multiple scion varieties

X

Pollinizer branch

X

Influence growth phase

Avoid undesirable rejuvenation

Induce desirable rejuvenation

Virus indexing

Exploit specific rootstock and/or interstock effects

Hybrid seed production of self incompatible species

How to Cleft Graft

Left: Splitter end of the cleft grafting tool is centered and struck with a hammer to split stock.

Right: Base of scion cut to a V-shaped wedge for insertion into the stock

Basal end of scion cut to a V-shape. Spreader end of the tool is used to pry open the split in the stock while inserting scion. Carpentry itself generates pressure, so tying is not necessary.

Slides 18 and 19 of this autotutorial describe the use of cleft grafting for changing over from an older to a newer apple variety on donor trees, from which scions are collected for field budding. There is a link to the first page of the autotutorial at the bottom of the page.